RXJAVA-concat

concat操作符可以连接俩个Observable，只有第一个Observable调用了onComplete后，才会触发第二个Observable。

比如在读取数据时，先查询缓存，缓存存在直接处理，不存在查询数据库，然后在处理。

package com.netty.demo.vertx;

import io.reactivex.*;
import io.reactivex.disposables.Disposable;
import io.reactivex.functions.Consumer;
import io.reactivex.functions.Function;
import io.reactivex.schedulers.Schedulers;
import lombok.extern.slf4j.Slf4j;
import org.reactivestreams.Subscriber;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
import java.util.concurrent.TimeUnit;

@Slf4j
public class RxJavaTest {

    public static void main(String[] args) throws InterruptedException {

        Observable o1 = Observable.create(new ObservableOnSubscribe<Integer>() {
            @Override
            public void subscribe(ObservableEmitter<Integer> emitter) throws Exception {
                //查询缓存数据
                Integer cacheData = Integer.MAX_VALUE;
                if (cacheData != null) {
                    //缓存不为空则直接传递给观察者
                    emitter.onNext(cacheData);
                } else {
                    //缓存为空则调用onComplete，触发第二个(o2)的执行逻辑
                    emitter.onComplete();
                }
            }
        });

        Observable o2 = Observable.create(new ObservableOnSubscribe<Integer>() {
            @Override
            public void subscribe(ObservableEmitter<Integer> emitter) throws Exception {
                //查询数据库
                Integer cacheData = Integer.MAX_VALUE;
                //传递给观察者
                emitter.onNext(cacheData);
            }
        });

        Observable.concat(o1, o2).subscribe(new Observer<Integer>() {
            @Override
            public void onSubscribe(Disposable d) {
                log.info("onSubscribe");
            }
            @Override
            public void onNext(Integer o) {
                log.info(o.toString());
            }
            @Override
            public void onError(Throwable e) {
                log.info("onError");
            }
            @Override
            public void onComplete() {
                log.info("onComplete");
            }
        });


        Thread.sleep(300000000);
    }
}